It wasn't your stuff was it?
Options -
Start singing "dude looks like a lady" when you see him
Bring it up at a big family gathering.
When the guys are hanging out having a beer, come in dancing with his wig and sing "Man, I feel like a woman".
Next time he comes over, answer the door in torn fishnets, combat boots, and a VC bra.
When you two are hanging out, start asking to borrow tools. "Yeah I was doing a head gasket and wanted to know if I could borrow that 1/2 drive 5/8 impact socket, you know the one right next to your purple teddy". Just say it with total indifference. then he might correct you and say real quick "BITCH that teddy is fuschia, learn your colors!"
OK maybe not the best ideas.
Look, don't say anything about finding it, not yet anyways. But I think it might be safe to come out. It will be an akward coming out as he will immediately think of his own trannyness.
Best case scenario - You two will come out to each other and then you two can be brothers AND sisters.
Worst case - he might want you to two to have some "you time" in your best lingerie.
I imagine he will probably show you his toolbox. Did he have any plastic tools in there?
Ehh I better scurry off now....